Telephone are linked through telecommunication systems that includes the public switched telephone network (PSTN), which is continually being improved thorugh such developments as the Advanced Intelligent Network (AIN). Devices that are linked through the PSTN with the aid of the AIN include conventional telephones, radio telephones (often referred to as cordless phones), answering machines, facsimile (fax) machines, computers, and computer peripherals such as modems, printers and the like. These devices in most cases are physically linked to the PSTN through copper wire and in some cases fiber optic lines. Thus, these devices are referred to herein as “wireline” or “landline” devices. A telecommunications system such as the PSTN that serves wireline devices is referred to herein as a “wireline” or “landline” network.
A wireline device, as its name implies, keeps its user tied to a particular geographic location through a line connected to a wireline network. For example, a wireline device in a person's home or office may be used only in the limited area of that home or office. Based on this tie to a particular geographic location, a subscriber's directory number in the wireline network generally is associated with the particular geographic location of the wireline devices used by the subscriber.
To break this tie to a particular geographic location, wireless telecommunications devices for use in wireless networks have been developed. A wireless telecommunications device is also referred to herein as a “wireless unit” or a “mobile unit”. The most familiar wireless units are cellular phones, which are also referred to as mobile phones and, when used in a car, as car phones. But wireless units may include other communication devices that operate on principles of radio or microwave technology. The most familiar types of wireless networks include the cellular mobile radio telephone (CMR) system and the personal communication network (PCN).
A wireless unit does not fetter its user with ties to a particular geographic location. Rather, a wireless unit may be used anywhere within a geographic area served by the subscriber's wireless network or by another wireless network through arrangements for such service made with the subscriber's wireless network. Based on the mobile nature of a wireless unit, a call to a subscriber using a wireless unit is directed to a number that is associated with the wireless unit. In the CMR system, this number is often referred to as a subscriber's “cell phone number” or “mobile phone number.”
Given the convenience of wireless units, their popularity is growing. But it is not yet an exclusively wireless world. For various reasons, including those of cost, infrastructure, and special services, a user may be a subscriber of both a landline service and a wireless service. For example, a salesperson may use a landline device in his or her home or office and may use a wireless unit in his or her car. In many cases, a subscriber's landline service is completely separate from the subscriber's wireless service. Where these services are separate, to reach a particular subscriber, a caller may have to call both the subscriber's landline directory number, which is associated with a particular geographic location, and the number which is associated with the subscriber's mobile unit. Trying to reach a subscriber by making two calls to two different numbers is inconvenient and inefficient. It is also inconvenient and inefficient to burden the subscriber with having to distribute more than one number to potential callers. It is further inconvenient and inefficient to burden a potential caller with having to know both of the numbers associated with the subscriber.
To overcome the problems associated with a subscriber having to use a landline device with a landline number and a wireless unit with a wireless number, some subscribers have made use of call forwarding services offered by the service providers of the landline service or the wireless service. For example, a subscriber may implement a call forwarding service with respect to his or her wireless number so that, for a time, all calls directed to the wireless number are forwarded to the landline number. A disadvantage of such an implementation of the call forwarding service is demonstrated in the case of a caller making a call from a wireless unit to the subscriber's landline number. The call is routed from the wireless network in which the caller's wireless unit is operating to the landline network in which the subscriber's landline device is located. But as noted, the subscriber's landline number has a call forwarding service implemented on it so that calls are forwarded to the subscriber's wireless unit. So, in this example, the call from the caller using the wireless unit is routed back from the landline network in which the subscriber's landline device is located to the wireless network in which the subscriber's wireless unit is located. This back-and-forth routing of a call from a first network to a second network and then back to the first network is known as “tromboning” or the “tromboning effect”.
FIG. 1 illustrates a case of tromboning with respect to a call that is routed from the landline network 12 to the wireless network 14 and back to the landline network 12. In this second example, assume a subscriber has implemented the call forwarding service on his or her wireless number associated with wireless unit 28d so that all calls to the wireless number are forwarded to the subscriber's landline number (associated with landline unit 16d). Also assume that a caller uses his or her landline device 16a to dial a call to the subscriber's wireless number. The call originates in the landline network 12 and is routed from the caller's landline unit 16a as indicated by arrow A through the service switching point (SSP) 18a and as indicated by arrow B to access tandem 20. From the access tandem 20, the call is routed to the wireless network 14, and in particular, through the access tandem 20 as indicated by arrow C to the mobile telephone switching office (MTSO) 22 serving the wireless number.
As a result of the implementation of the call forwarding service on the wireless number, a check of the home location register (HLR) 24, as indicated by arrows D and E, results in forwarding of the call from the subscriber's wireless number to the subscriber's landline number. Thus, the call is routed from MTSO 22 as indicated by arrow F through access tandem 20 and back to the landline network 12. In particular, from access tandem 20, as indicated by arrow G, the call is routed to the SSP 18b which serves the subscriber's landline number. From the SSP 18b, as indicated by arrow H, the call is terminated to the wireline device 16d associated with the subscriber's landline number. Thus, the call suffers from the tromboning effect by being routed: (1) from the landline network 12 to the wireless network 14 as indicated by arrows A, B, and C; and (2) back from the wireless network 14 to the landline network 12 as indicated by arrows D, E, F, G, and H.
In this example, tromboning occurs with respect to this call for the following reasons: (1) the call originates in a first network; (2) the information with respect to the call forwarding service is located in a second network; and (3) the call forwarding information indicates that the call is to be routed back to the first network. In other words, the call has to cross from the first to the second network so as to obtain the information that the call must double back to the first network.
The tromboning of a call adversely impacts the call because the back-and-forth routing of the call from one network to another and back to the first network results in a delay in the processing of the call. In addition, the tromboning of a call has negative consequences on the networks that are involved in the back-and-forth routing of the call, because the tromboning detrimentally occupies network resources that otherwise could be used to handle other traffic.
The tromboning effect and its problems have been described in the context of back-and-forth routing between a landline network and a wireless network that results from the implementation of a call forwarding service. But the tromboning effect may occur between any two communication networks where a call or other communication originates with a first network, is routed to a second network, and then is re-routed for termination or connection to a unit operating in the first network.
Accordingly, there is a need for a method and system that overcomes the problems associated with a telecommunications subscriber having to keep track of two different numbers and possibly having to dial two different numbers (a landline number and a wireless number) to reach a subscriber who utilizes both landline service and wireless services.
There is also a need for a method and system that prevents the tromboning effect with respect to the routing of a call or other communication from a first device to a second device.
There further is a need for a method and system that prevents the tromboning effect with respect to the routing of a call or other communication between two communication networks wherein a call or other communication originates with a first network, is routed to a second network, and then is re-routed for termination or connection to a device operating in the first network.